Noise-optimized device for injecting fuel

ABSTRACT

The invention relates to a unit injector system for supplying the combustion chamber of a self-igniting internal combustion engine with fuel. The unit injector system has a high-pressure chamber that can be subjected to pressure via a pump piston. A storage piston is received inside a storage chamber and is acted upon via a compression spring disposed in a spring holder. A return flow throttle element, which delays the buildup of pressure in the storage chamber, is disposed between the high pressure chamber and the storage chamber of the storage piston.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In systems for injecting fuel into the combustion chamber of internalcombustion engines, component parts such as switching valves andinjection nozzles in high-pressure pumps and in the various embodimentsof injectors, nozzle holder combinations, or unit injector systems aremade to move. Their motion positively displaces a volume which isreplenished on the intake side. For the requisite volumetric flow, thepressures and cross sections must be adapted. If the replenishment offuel is inadequate, the pressure on the intake side drops. If the vaporpressure of the fluid to be pumped fails to be attained, the column ofliquid breaks off, causing cavitation bubbles to form. Uponrecompression of the fuel to above the vapor pressure, the collapse ofthe vapor bubbles causes noise.

2. Description of the Prior Art

With present unit injector systems in self-igniting internal combustionengines, mechanically-hydraulically controlled preinjection phases aregenerated, which contribute on the one hand to reducing the noise ofcombustion and on the other to minimizing pollutants. In unit injectorsystems, a distinction can be made among four operating states. A pumppiston is moved upward via a restoring spring. The fuel, which is at aconstant overpressure, flows out of the low-pressure part of the fuelsupply via the inlet bores, which are integrated with the engine block,and via the inlet conduit into the magnet valve chamber. The magnetvalve is opened. Via a connecting bore, the fuel reaches thehigh-pressure chamber.

Upon a rotation of the driving cam, the pump piston moves downward. Themagnet valve remains in its open position, and the fuel is forced by thepump piston via the inlet conduit back into the low-pressure part of thefuel supply.

In a third phase of the injection event, an actuator is triggered by thecontrol unit at a specified instant, so that the actuator is pulled intoa seat, and the communication between the high-pressure chamber and thelow-pressure part is closed. This instant is also known as the“electrical injection onset”. The high fuel pressure in thehigh-pressure chamber rises continuously as a result of the motion ofthe pump piston, and as a result a rising pressure is also establishedat the injection nozzle. Once a nozzle opening pressure is reached,lifting of the nozzle needle occurs, causing fuel to be injected intothe combustion chamber. This instant is also called the “actualinjection onset”, or the supply onset. Because of the high pumping rateof the pump piston, the pressure continues to rise during the entireinjection event. In a concluding operating state, the actuator is turnedoff again, after which the actuator opens after a slight delay, and thecommunication between the high-pressure chamber and the low-pressurepart is opened again. As the actuator, magnet valves or piezoelectricactuators can for instance be used.

In this transition phase, the peak pressure is reached. After that, thepressure collapses very quickly. When it falls below the nozzle closingpressure, the injection nozzle closes and terminates the injectionevent. The remaining fuel pumped by the pump element until the apexpoint of the driving cam is forced into the low-pressure part via thereturn conduit.

Single-pump systems of the kind described above are intrinsically safe;that is, in the unlikely event of a fault or defect, no more than oneuncontrolled injection can occur: If the magnet valve opens, injectioncannot occur, since the flows back into the low-pressure part, and apressure buildup cannot occur. Since the filling of the high-pressurechamber takes place exclusively via the actuator, when the actuatorremains constantly in the closed state no fuel can reach thehigh-pressure chamber. As a rule, unit injector systems are built intothe cylinder head and exposed to high temperatures. To keep thetemperatures in the unit injector system as low as possible, cooling ofthe components of the unit injector system is as a rule done by means offuel, which in turn flows back into the low-pressure part of the fuelinjection system.

The total pressure p_(tot) of a flowing medium is composed of a staticpressure component p_(stat) and a dynamic pressure component p_(dyn).Except for pressure losses, caused for instance by friction, the totalpressure established is constant. The kinetic pressure, conversely, isproportional to the square of the flow velocity, in accordance with thefollowing equation: $P_{d\quad{yn}} = {\frac{\rho}{2}v^{2}}$

If the fuel in the pump of the unit injector system is acceleratedsharply, the static pressure drops. In the process, it can drop belowthe vapor pressure, resulting in cavitation.

In the motion of the storage piston, both phenomena can occur. Themotion of the storage piston leads to a compression of the fuel in thespring holder. This increases the counterpressure of the injectionnozzle, which leads to the end of the preinjection phase. In addition,the compression increases the second opening pressure for the subsequentinjection. To assure good emissions outcomes, fast opening of thestorage piston is indispensable. From an acoustical standpoint, however,the fast opening is not critical, since then the intake sidecommunicates with the element chamber, in which at this instant highpressure still prevails. Upon the return motion of the storage piston,the positively displaced volume must return into the spring holder. Thisreturn flow is effected either via a communication with the return, or acommunication with the inflow loop. In the process, the fuel passesthrough a throttle, whose cross section has a certain value. If thethrottle is enlarged, a residual pressure can be maintained as afunction of the flow cross section. If the positively displacedvolumetric flow is greater than the replenishing quantity, then thepressure in the spring holder drops. If when the pressure in the springholder drops it drops below the vapor pressure, cavitation can occur.

In the return motion of the storage piston at the end of the injectionevent, the column of liquid above the storage piston is moved in thedirection of the element chamber. At this instant, the pressure in theelement chamber is already close to the vapor pressure, and as a resulta fast return flow can occur. The high flow velocity can lead toundershooting of the vapor pressure so that once again cavitation can bethe result.

European Patent Disclosure EP 0 404 916 B1 has a fuel injection nozzleas its subject. The fuel injection nozzle, embodied in particular as apump-nozzle, includes a nozzle needle, which is urged in the closingdirection by a spring. In the fuel injection nozzle, a pressure chamberupstream of the seat of the nozzle needle is in communication with astorage chamber that is defined by a spring-loaded compensation piston.The compensation piston (also called a storage piston), with its storagepiston bush, forms a sealing seat. The storage chamber is locateddownstream of this sealing seat, as viewed from the pressure chamber.The storage piston, which has a cylindrical guide part, is subjected, onits end remote from the storage chamber, to the pressure in a dampingchamber that can be filled with fuel, and it has a peg which dips into aplate that defines the damping chamber and has an opening. Thecylindrical guide part of the storage piston has a ratio of the diameterto the height of 1:0.1 to 1:0.4; the peg of the storage piston has avariable cross section that dips into the boundary plate, and on its endtoward the storage chamber, the storage piston has a guide extensionwith grooves.

OBJECT AND SUMMARY OF THE INVENTION

In the proposed embodiment, a delay in the storage piston return motioncan be achieved, yet without significantly impairing the opening motionof the storage piston inside a unit injector system. To that end, areturn flow throttle valve can be disposed in the region of thehigh-pressure communication of the storage chamber.

The return flow throttle valve is passable, viewed in the openingdirection of the storage piston, so that the hydraulically controlledpreinjection is unimpaired. After the end of the main injection, thehigh-pressure in the entire high-pressure volume drops so far that theclosing pressure level of the storage piston is reached. When theclosing pressure level is reached, the closing motion of the storagepiston begins. If a return flow throttle valve is used, a pressuredifference is established between the pressure on the storage pistonside of the return throttle and the pressure on the high-pressure side,and this pressure difference causes a closure of the return throttle. Apressure reduction can in this case only occur in delayed fashion viathe throttle restriction itself, so that the return motion is sloweddown sharply.

By the design of the seat cross section, the stroke, the throttle crosssection, and the spring adaptation of the return flow throttle element,the reverse motion of the storage piston, that is, the component motionthat is definitive for the cavitation phenomena, can be delayed to suchan extent that a replenishing flow of fuel into the interior of thespring holder occurs without cavitation, so that noise does not develop.

Instead of a return flow throttle valve, a check valve can be used inthe unit injector system. Toward the end of the injection, the pressureon the high-pressure side drops, whereupon the check valve closes. Thepressure in the reservoir remains at a high level, so that the storagepiston remains in its open position. Leaks for production and tolerancereasons at the storage piston guide causes slow reduction in thepressure, until it drops below the closing pressure of the reservoir,and the storage piston closes slowly.

If the pressure always remains above the vapor pressure during therefilling of the hollow spring holder chamber, cavitation phenomena canbe avoided, which favorably affects the noise developed in this kind ofunit injector system.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood and further objects andadvantages thereof will become more apparent from the ensuing detaileddescription of preferred embodiments taken in conjunction with thedrawings, in which:

FIG. 1 shows the general layout of a unit injector system for supplyingfuel to the combustion chambers of a self-igniting internal combustionengine;

FIG. 1 a is an enlarged view of the fluidic communication between thestorage chamber and the hollow chamber of the spring holder in the priorart shown in FIG. 1;

FIG. 2 shows the return flow throttle unit, disposed between the storagepiston chamber and the hollow spring holder chamber, for delaying theclosing motion of the storage piston;

FIG. 3 shows the storage piston in its closed position;

FIG. 4 shows the opening of the sealing seat of the storage piston whenits opening pressure is reached; and

FIG. 5 shows the sealing off of a hollow chamber in the injector by anend face facing the sealing seat of the storage piston.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the unit injector system shown in FIG. 1, a pump piston 3, which isreceived movably in a pump body 4, is actuated via a spherical bolt 1.The spherical bolt 1 in turn is actuated via a tiltably disposed tiltlever 28, which is provided on one of its ends with a rotatablysupported roller body. The roller body rolls along a cam of a drivingcamshaft 27. The deflection of the tilt lever 28 about its pivot axisdepends on the course of the shaping of the top of the cam, which in theview of FIG. 1 extends eccentrically to the pivot axis of the drivingcamshaft 27.

The pump piston 3 of the pump body 4 of the unit injector system isacted upon by a restoring spring 2, which is braced on one end on aplane face of the pump body 4 and on the other on a caplike supportelement, which is disposed in the upper region of the pump piston 3 thatis movable in the pump body 4.

Laterally of the pump body 4 is an actuator, which in the exemplaryembodiment shown in FIG. 1 includes a magnet coil 10. The magnet coil 10of the actuator acts on an armature 9, which in turn acts on a magnetvalve needle. The armature 9 of the actuator is acted upon by acompensation spring 7. Reference numeral 6 indicates the magnet core,which surrounds the magnet coil 10 of the actuator.

A fuel return 11 is shown below the actuator; by way of it, excess fuelflowing out of the unit injector system can return into a low-pressureregion, not further shown in FIG. 1, such as the tank of a motorvehicle. In the fastening region at the cylinder head of the engine, theunit injector system is sealed off by way of sealing elements 12. Insidethe unit injector system, inlet bores 13 are embodied in the wall, andby way of them fuel flows from a low-pressure-side fuel forward flow, toa valve chamber of an actuator, embodied here as a magnet valve, to theelement chamber 25. As a result of the pressures applied, fuel isconducted through the pump body 4 for cooling the actuator and, via abore system embodied in the pump body 4, it reaches a chamber defined bytwo sealing rings 12, and from there it is carried away via the fuelreturn marked 11. Via the fuel return in the unit injector system asshown in FIG. 1, the leak fuel in the pump piston 3 can be carried away;moreover, by means of throttle restrictions embodied in the returnsystem, vapor bubbles can be removed.

Reference numeral 14 indicates a hydraulic stop, which functions as adamper. Extending below the hydraulic stop is a nozzle needle 18, whichis partly surrounded by an integrated injection nozzle body 20. Thenozzle needle 18, in its front region pointing toward a combustionchamber 17, is seated inside a needle seat 15. By means of a lock nut19, the unit injector system and the integrated injection nozzle 20partly surrounding the nozzle needle 18 communicate with one another;below the lock nut 19, there is a sealing disk 16, for sealing off thecombustion chamber 17 of a self-igniting internal combustion engine fromthe cylinder head of the engine. The cylinder head of the self-ignitingengine is marked 21.

Within the unit injector system as shown in FIG. 1, a hollow chamber 42of a spring holder is provided, which receives a compression spring 22,embodied for instance as a spiral spring. The compression spring 22 isbraced by its lower end on a disklike insert in the hollow chamber 42 ofthe spring holder, and with its opposite end it acts on a storage piston23. The storage piston 23, embodied for instance in two parts, includinga peglike element and a disk, is enclosed inside the unit injectorsystem by a storage chamber 24. The disk can be embodied as a separatecomponent. The storage chamber 24 of the storage piston 23 and thehollow chamber 42 of the spring holder are in fluidic communication withone another, via an opening 31 shown enlarged in FIG. 1 a.

The pump piston 3, which is movable vertically up and down via the tiltlever 28, acts upon a high-pressure chamber 25 within the unit injectorsystem, which is also known as an element chamber. Below the disklikecomponent that demarcates the high-pressure chamber 25, a high-pressureinlet branches off to the nozzle chamber and acts upon the nozzle needle18 on the end toward the cylinder head of the unit injector system. Fromthe nozzle chamber, the fuel, which is at high pressure, flows via anannular gap in the direction of the needle seat 15, and from there, uponan upward motion of the nozzle needle 18, it is injected into thecombustion chamber 17 of the self-igniting engine within a preinjectionand a main injection.

For the sake of completeness, it should be noted that reference numeral26 indicates a magnet valve spring, which urges the magnet valve needle8 in the restoring direction.

In FIG. 1 a, an enlarged view of the region of the unit injector systemshown in FIG. 1 can be seen, in which the opening 31 between the storagechamber and the hollow chamber of the spring holder is shown on a largerscale.

As can be seen from the view in FIG. 1 a, the storage piston 23 issurrounded by the storage chamber 24 and is acted upon by fuel, which isat high pressure, from the high-pressure side that is emerging from thehigh-pressure chamber 25. By the downward motion of a face end 29 of thestorage piston 23, as it is acted upon by high pressure via thehigh-pressure chamber 25, the fuel in the hollow chamber of the springholder 42 is compressed. As a result, the counterpressure on theinjection nozzle increases, bringing about an end of a preinjectionphase. To assure high-quality emissions outcomes, fast opening of thestorage piston 23 is required. Upon fast opening of the storage piston23, the intake side of the storage piston 23 is in communication withthe high-pressure chamber 25. At that instant, high pressure prevailsinside the high-pressure chamber 25.

In the return motion of the storage piston 23, the positively displacedvolume must return into the hollow chamber 42 of the spring holder. Thiscan be done either via a communication with the return or at the inflowloop. If the positively displaced fuel volume is greater than thereplenished quantity, the pressure in the hollow chamber 42 of thespring holder drops. If it drops below the vapor pressure, cavitationoccurs. Also in the return motion of the storage piston 23 at the end ofan injection event, the liquid column above the storage piston 23 ismoved in the direction of the high-pressure chamber 25. At that instant,the pressure inside the high-pressure chamber 25 is already in thevicinity of the vapor pressure, and as a result a fast return flowoccurs. The high flow velocity of this return process causes thepressure to drop below the vapor pressure, and thus can once again causecavitation.

FIG. 2 schematically shows a return flow throttle element, disposedbetween the storage chamber and the hollow chamber of the spring holder,for delaying the motion of the storage piston.

FIG. 2, in highly simplified form, shows a return flow throttle valve35, which is disposed between the storage chamber 24 of the storagepiston 23 and the element chamber 25 of the spring holder. By means ofthe return flow throttle valve 35, the possibility exists of slowingdown the return motion of the storage piston 23, without substantiallyaltering the opening motion, which should occur with the least possiblehindrance, of the storage piston 23. The return flow throttle valve 35,which is shown schematically in the view in FIG. 2, includes a valvebody 37, which is acted upon by a spring element 36, and a permanentlyoperative throttle restriction 44, by way of which the storage chamber24 of the storage piston 23 and the element chamber 25 are in fluidiccommunication with one another.

Once the pressure difference between the element chamber 25 and thestorage chamber 24 of the storage piston 23 has caused the return flowthrottle valve 35 to close, the pressure in the storage chamber 24slowly decreases in the direction of the element chamber 25. Because ofthe slow decrease, the motion of the storage piston 23 inside thestorage chamber 24 is slowed down, so that replenishing fuel, forinstance from the inlet bores 13, can flow fast enough into the hollowchamber 42 of the spring holder B fast enough that the pressure theredoes not drop below the vapor pressure. If the pressure is kept abovethe vapor pressure there, no cavitation occurs, and so cavitation-freeoperation can be achieved.

The return flow throttle valve 35 allows an unhindered opening motion ofthe storage piston 23 in the storage chamber 24, since the return flowthrottle valve 35 is passable in the second direction 40. After the endof the injection, the high pressure in the entire high-pressure volume,that is, inside the element chamber 25, drops so far that the closingpressure of the storage piston 23 is reached, and its closing motionbegins. Because of a pressure difference that arises between thepressure on the reservoir-side end of the return flow throttle valve 35and the pressure on the high-pressure side of the return flow throttlevalve 35, that is, on the side pointing toward the element chamber 25,the return flow throttle valve 35 closes.

When a return flow throttle valve 35 with a throttle restriction 44 isused, only the throttle restriction 44 remains open after the closure ofthe closing element 37; the pressure reduction can be varied by means ofhow this throttle restriction is designed in terms of the flow crosssection. Delaying the pressure reduction in the direction of the elementchamber 25 delays the motion of the storage piston 23 inside the storagechamber 24. Because of the delayed course of the return motion of thestorage piston 23, refilling of the hollow chamber 42 of the springholder B takes place via inlet bores 13 in such a way that in thisregion no cavitation occurs, since the pressure can be kept above thevapor pressure level.

By means of the design of the seat cross section 38 at the return flowthrottle valve 35, its stroke, and the design of the throttle crosssection of the throttle restriction 44 and the spring prestressing bythe spring element 36, the motion of the storage piston 23 can be sloweddown to such an extent that the refilling of the hollow chamber 42 ofthe spring holder takes place in a way that avoids cavitation.

FIG. 3 shows a storage piston in its closing position on the sealingseat.

It can be seen from FIG. 3 that the storage piston 23 has moved by astroke length 41 into its sealing seat 34 toward the element chamber 25.The hollow chamber 42 of the spring holder B is in communication, viathe opening 31, with part of the storage chamber 24, and an end face 29on the underside of the storage piston 23 has been placed at thedistance of the stroke length 41 from the bottom of the storage chamber24, in the position shown in FIG. 3. In this position of the storagepiston 23, the storage piston disconnects the element chamber 25 fromthe storage chamber 24.

FIG. 4 shows the opening of the sealing seat at the storage piston whenits opening pressure is reached. When the opening pressure level of thestorage piston 23 is exceeded, the sealing seat, marked 34, on the topof the storage piston 23 opens. The storage chamber 24 of the storagepiston 23 is now filled via the opened sealing seat 34 and via theelement chamber, and the storage piston 23 moves in the direction of thehollow chamber 42 of the spring holder B.

FIG. 5 shows the sealing off of the hollow chamber of the spring holderB by an end face, facing the sealing seat, of the storage piston.

It can be seen from FIG. 5 that the end face 29 of the storage piston 23rests on the opening 31 that connects the storage chamber 24 and thehollow chamber 42 of the spring holder B to one another. From FIG. 5, itcan be seen that the storage piston 23 now seals off the storage chamber24, which in turn is in communication with the element chamber 25, fromthe hollow chamber 42 of the spring holder B.

In terms of the design of the seat cross section 38 of the return flowthrottle valve 35 and of the stroke length 41 of the storage piston 23,these should be designed such that the opening motion of the storagepiston 23, in the phase shown in FIGS. 4 and 5, should proceed virtuallyunhindered. In the opening phase of the storage piston 23 in thedirection marked 40 in FIG. 2, the storage chamber 24 is filled first,and after it, the volume that results from the product of the storagepiston end face 29 and the stroke length 41 of the storage piston.Design:$V_{total} = {V_{{storage}\quad{chamber}\quad 24} + \left( {\frac{{\pi\quad\varnothing\quad{end}\quad{face}\quad 29^{2}}\quad}{4} \times h_{{storage}\quad{piston}}} \right)}$

Calculating the reservoir volume from the seat face area and the strokelength depends on how the valve is designed, for instance whether a coneseat or a ball seat is involved, which can mean different seat facediameters or averaged seat face diameters.

It is advantageous to select as short as possible a stroke length of thereturn flow throttle valve 35, or of an alternatively usable checkvalve, so that the entire opening cross section can already be attainedafter only a brief opening time.

In terms of the design of the spring element 36 of the return flowthrottle valve 35, the goal is to design the spring prestressing of thespring element 36 such that the return flow throttle valve 35 can bekept in a defined prestressed position in the pressureless state, and afast closing motion is reinforced upon closure of the return flowthrottle valve 35.

The task of the throttle cross section of the throttle restriction 44embodied on the return flow throttle valve 35 is to slow down thepressure relief of the storage chamber 24 in the direction of theelement chamber 25 in such a way that no cavitation occurs in the hollowchamber 42 of the spring holder B. On the other hand, a pressure reliefof the storage chamber 24 in the direction of the element chamber 25should be attained that is fast enough that at the onset of the nextinjection cycle, the original pressure ratios, or in other words, apressure equilibrium, is established soon enough.

In a further variant embodiment of the concept on which the invention isbased, a check valve can be used. The check valve, for instancecontaining a spherically shaped closing element 37, which is acted uponby a spring element, preferably a spiral spring 36, forms the limitshape of a return flow throttle element, in which the throttle is closedin the limit case. At the end of injection, the pressure in thehigh-pressure chamber 25 is subjected to high pressure by the pumppiston 3, in accordance with its reciprocating motion. With the checkvalve closed, the pressure on the reservoir side 24 remains at such ahigh level that the storage piston 23 stays in its opening position.From leakage at the storage piston guide, which necessarily occursbecause of production and tolerance reasons, the pressure slowly dropsuntil it falls below the closing pressure of the reservoir, and thestorage piston 23 slowly begins its closing motion. Depending on thepressure drop attainable, and because of a pressure reduction via theleakage gaps, the pressure buildup occurs so slowly that the refillingof the spring holder 42 proceeds such that the pressure level inside thehollow chamber of the spring holder 42 can be kept above the vaporpressure at all times, so that no cavitation can occur inside the hollowchamber 42 of the spring holder, and thus a considerable noise abatementcan be attained by avoiding vapor bubble formation in the fuel.

In both variant embodiments, that is, when a return flow throttle valveis used as the return flow throttle element and when a check valve isused as the return flow throttle element, it is attainable that by theintegration between the element chamber 25 and the storage chamber 24 ofthe storage piston 23, a delay in the restoring motion of the storagepiston 23 can be attained. By reducing the speed of motion of thestorage piston 23 within the unit injector system, a drop in thepressure level inside the unit injector system in the hollow chamber 42of the spring holder B to below the vapor pressure can be effectivelyprevented. Since with the embodiment proposed according to the inventionno vapor bubble formation or in other words cavitation can occur insidethe hollow chamber 42 of the spring holder B, a substantially quieteroperation of the unit injector system is possible when the embodimentproposed according to the invention is used, even in high rpm ranges ofthe unit injector system.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. A unit injector system for supplying the combustion chamber (17) of an internal combustion engine with fuel, having a high-pressure chamber (25) that can be subjected to pressure via a pump piston (3), and having a storage piston (23), received inside a storage chamber (24), that is acted upon via a compression spring (22) disposed in a spring holder chamber (42), characterized in that disposed between the element chamber (25) and the storage chamber (24) of the storage piston (23) is a return flow throttle element (35), which return flow throttle element (35) is passable in a second direction (40) corresponding to the opening direction of the storage piston (23), and characterized in that the return flow throttle element (35) reduces the closing direction of the storage piston (23) in a first direction (39) corresponding to the closing direction of a storage piston (23), so that the return flow throttle element delays the buildup of pressure in the storage chamber (24).
 2. The unit injector system of claim 1, characterized in that the return flow throttle element (35) is embodied as a return flow throttle valve.
 3. The unit injector system of claim 1, characterized in that the return flow throttle element (35) is embodied as a check valve.
 4. The unit injector system of claim 2, characterized in that at a pressure difference Δ_(p) that comes to be established above the return flow throttle element (35) between the element chamber (25) and the storage chamber (24), the return flow throttle element (35) closes in such a manner that a pressure reduction is now effected only via a throttle restriction (44) of the return flow throttle element (35).
 5. The unit injector system of claim 1, characterized in that a sealing seat (34) that opens or uncovers the element chamber (25) toward the storage chamber (24) embodied on the storage piston (23).
 6. The unit injector system of claim 1, characterized in that an end face (29) that closes an opening (31) of a hollow chamber (42) of a spring holder (B) is embodied on the storage piston (23), on the side oriented toward the hollow chamber (42).
 7. The unit injector system of claim 1, characterized in that a peg dips into the opening (31) to the hollow chamber (42) is embodied on the storage piston (23). 